In mixing fluent materials, particularly dry fluent solids, considerable difficulty is encountered in obtaining uniform compositions of the final mixes. The difficulties are partly attributable to variations in the particle sizes of the materials being mixed and sometimes to variations in densities of the materials. Even with utmost accuracy in proportioning and weighing of the ingradients, uniformity of the final product is difficult to obtain. Notwithstanding these difficulties, it is necessary in many operations and particularly in chemical analyses to obtain a product of a high degree of uniformity.
Various methods have been tried for insuring uniformity of the products. Many of the methods require expensive working and reworking of the material, a circumstance which in unacceptable by the present day highspeed operations of commerce, both from the standpoint of time consumed and the expense and energy required for such operations. If physical characteristics, for example, particle size, particle shape, particle density and the rheological properties of the materials vary widely among the various components, handling and processing equipment must be provided to cope with the most unfavorable combinations of such conditions.
In commercial operations, the type of blending employed will depend on such factors as the homogeneity requirements of the final product, variances in the physical and chemical properties of the components, the tendency of the components to segregate on storage and the like. When dry solids are mixed, as in the manufacture of fertilizers, the streams can be proportioned with a relatively high degree of accuracy. However, for bulk operations where the value of the product will not justify expensive mixing and blending equipment, uniformity of the product is frequently lacking. Some producers attempt to overcome non-uniformity of product by adding an overage of required components so that operational variations will be compensated for by the additional material. This is expensive from the standpoint of material which is given away. Furthermore, it is not always acceptable because some of the industry regulatory agencies will not permit overages above certain fixed limits just as they will not permit shortages. Thus, where variations are of considerable magnitude, it is not always possible to satisfy the requirements of the regulatory agencies by adding more material than would be required normally. For these reasons, it is desirable that more effective methods be found for achieving final blends of uniform composition.